[Nut-upsuser] UPS connection established, lost, established, etc.

[Robert McDonald]

I have an APC Back-UPS CS 500 which connects via USB. I am running NUT
2.4.1 under Karmic amd64. The entry in ups.conf is

[apc]
driver = usbhid-ups
port = auto
desc = "APC Back-UPS CS 500"

I left upsd.conf at the default values, nut.conf is "mode standalone",
and in upsmon.conf, the monitor line is

MONITOR apc at localhost 1 ups_local mypassword master

and in upsd.users,

[ups_local]
    password = mypassword
    upsmon master

I start nut with

sudo /etc/init.d/nut start; sudo upsdrvctl start

I am able to connect to the UPS, and the command "upsc apc" returns
the UPS characteristics, so the connection definitely works. However,
after a short period of time, the UPS connection is lost and then
regained, so I get a sequence of messages like this (from syslog):
Any suggestions for debugging this?

Feb 12 14:10:38 fin8344 upsmon[2336]: Communications with UPS
apc at localhost established
Feb 12 14:11:48 fin8344 upsd[2331]: Data for UPS [apc] is stale - check driver
Feb 12 14:11:50 fin8344 upsd[2331]: UPS [apc] data is no longer stale
Feb 12 14:12:58 fin8344 upsd[2331]: Data for UPS [apc] is stale - check driver
Feb 12 14:13:00 fin8344 upsd[2331]: UPS [apc] data is no longer stale
Feb 12 14:16:56 fin8344 upsd[2331]: Data for UPS [apc] is stale - check driver
Feb 12 14:16:58 fin8344 upsmon[2336]: Poll UPS [apc at localhost] failed
- Data stale
Feb 12 14:16:58 fin8344 upsmon[2336]: Communications with UPS apc at localhost lost
Feb 12 14:17:02 fin8344 upsd[2331]: UPS [apc] data is no longer stale
Feb 12 14:17:03 fin8344 upsmon[2336]: Communications with UPS
apc at localhost established

And then I sometimes get message like this relating to the driver:

Feb 13 13:59:18 fin8344 upsmon[15163]: Communications with UPS
apc at localhost lost
Feb 13 13:59:18 fin8344 usbhid-ups[15176]: Got disconnected by another
driver: Device or resource busy
Feb 13 13:59:18 fin8344 kernel: [85629.405233] usb 2-1.5: usbfs:
process 15176 (usbhid-ups) did not claim interface 0 before use

I have no idea where to begin looking for a configuration problem. Can
anyone offer suggestions? Thanks!

Bob